Separation control using synthetic vortex generator jets in axial compressor cascade

Proceedings of the Institution of Mechanical Engineers, Part A:

Gong

Wang

2017

Unsteady pulsed holed suction as a new unsteady flow control technique is first proposed. Unsteady excitation models of four different waveforms (Waveforms 1, 2, 3, and 4) based on unsteady pulsed holed suction are investigated to analysis comparatively the control effects of flow separations in a certain highly loaded compressor. Some related unsteady aerodynamic parameters such as excitation frequency and excitation location are studies. The unsteady pulsed holed suctions of the four different modes (Waveforms 1, 2, 3, and 4) all effectively control flow separations. Their optimum frequencies are all an integer multiple of the natural frequency of vortex shedding. And their excitation locations gaining positive effect and optimal excitation locations are both same. The optimal excitation location is near the separation point of upper endwall in unexcited case. But, they show markedly different performances in reducing the total pressure losses. The unsteady pulsed holed suction of Waveform 3 shows greater advantage at different excitation frequencies and excitation locations. The optimum result is obtained by the unsteady pulsed holed suction of Waveform 3. The total pressure loss is reduced by 16.8%. Simultaneously, the unsteady pulsed holed suctions of the four different modes all can provide better effects than the steady constant holed suction in reducing the total pressure loss with the same suction-to-inlet time-averaged suction flow ratio ms. Especially at ms = 0.29%, for the steady constant holed suction, it is too small to effectively control flow separation, and consequently the total pressure loss are increased by 8.3%. However, for the unsteady pulsed holed suctions of Waveforms 2 and 3, the total pressure losses are reduced by 9.1% and 4.3%, respectively.

Section: The Effect Of Excitation Locationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Flow control using unsteady pulsed holed suction with different excitation models in a highly loaded compressor cascade

Proceedings of the Institution of Mechanical Engineers, Part A:

Gong

Wang

2017

Flow Turbulence Combust

“…Among other control devices the synthetic jet (SJ) seems to be attractive for future aero-engine applications [4,5]. One of the most appealing features of this device is the possibility of inducing momentum transfer from the outer to the inner part of the boundary layer without consumption of mass flow.…”

Section: Introductionmentioning

confidence: 99%

Application of a Synthetic Jet to Control Boundary Layer Separation under Ultra-High-Lift Turbine Pressure Distribution

Lengani

Simoni

Ubaldi

et al. 2011

The transition and separation processes of the boundary layer developing on a flat plate under a prescribed adverse pressure gradient typical ofUltra-High-Lift low-pressure turbine profiles have been investigated, with and without the application of a synthetic jet (zero net mass flow rate jet). A mechanical piston has been adopted to produce an intermittent flow with zero net mass flow rate. The capability of the device to suppress or reduce the large laminar separation bubble occurring under steady inflow condition at low Reynolds numbers has been experimentally investigated by means of hot-wire measurements.Wall static pressure measurements complement the hot-wire time-resolved velocity results. The paper reports the investigations performed for both steady and controlled conditions. The active device is able to control the laminar separation bubble induced at low Reynolds number conditions by the strong adverse pressure gradient. An overall view of the timedependent evolution of the controlled boundary layer is provided by the phaselocked ensemble averaging technique, triggered at the synthetic jet frequency. The separated flow transition process, which is detected for the uncontrolled condition, is modified by the synthetic jet in different ways during the blowing and suction phases. Overall, the phase-locked velocity distributions show a reduced separated flow region for the whole jet cycle as compared to the uncontrolled condition. The phase-locked distributions of the random unsteadiness allow the identification of vortical structures growing along the shear layer mainly during the blowing phase

“…12,13 An experimental investigation conducted in a high-speed cascade wind tunnel by Zheng et al. 14 demonstrated that synthetic vortex generator jets (VGJs) can improve the aerodynamic performances and reduce loss coefficient up to 22.8%. Evans et al.…”

Section: Introductionmentioning

confidence: 99%

Effect of the end-wall vortex generator jets on the performance of a high subsonic compressor cascade

Liu

Proceedings of the Institution of Mechanical Engineers, Part A:

2018

This paper presents a numerical and experimental result of the end-wall vortex generator jets for controlling corner separation and enhancing the aerodynamic performance in a high subsonic (Ma = 0.7) compressor cascade. The experiments were carried out on a compressor cascade at design point ( i = 0°) and off-design points ( i = −2°, 2°, and 4°). At design point, the total pressure loss coefficient could be reduced up to 12.1%.With the increase in the incidence, the control effect is enhanced first and then reduced. The maximum total pressure loss reduction is up to 14.6% when the incidence is 2°. The numerical study is further conducted to analyze the flow pattern and the vortex structure. The jet vortex is formed downstream of the jet hole using the vortex generator jets, the cross flow on the end wall is also suppressed.